1. Field of the Invention
The present invention relates to a display device, and more particularly to a display device which is able to automatically display a 3D image by the use of two microretarders and a polarizer to form a parallax barrier. Furthermore, with the relative movement of the microretarders, switching between 2D and 3D images and viewer-tracking are accomplished.
2. Description of Related Art
Conventional displays have developed dramatically from black and white to color. Nowadays, displays with high quality images are the current trend. Therefore, watching a 3D image without wearing additional accessories will be the next trend of display technologies. However, before all the displays have the feature to show a 3D image, thus, how to incorporate this 3D displaying feature into the current specification of an existing displays is vital for achieving the expectations and aspirations of the public.
Using a parallax barrier to separate the images received respectively by the left eye and the right eye of a human is well known in the art. U.S. Pat. No. 725,567 (1903) has already disclosed this technique. U.S. Pat. No. 5,831,765 used this well-known technique to place a parallax barrier (93) between a liquid crystal display (LCD) panel (91) and a back light (94) to form a 3D display. The improvement of this patent is that a dispersed type LCD panel (92) which is able to switch between dispersive and transparent modes is inserted between the LCD panel (91) and the parallax barrier (93) to show 2D and 3D images respectively
With reference to FIG. 6, the shortcoming of this method is:
{circle around (1)} The brightness of the LCD panel is reduced by half.
{circle around (2)} The distance between the barrier and the LCD panel is increased, which is unsuitable for the design where the lateral width of the liquid crystal pixel is small and the watching distance is close.
{circle around (3)} The dispersed type LCD panel is expensive so that the overall cost of the display is increased.
{circle around (4)} Non-continuous viewer tracking. If the viewer moves from one position to another, the viewing angle is thus changed, which results in the 3D image is not perceivable.
U.S. Pat. No. 6,157,424, includes an LCD panel (91′), a striped LC parallax barrier (93′) and a back light (94′), also uses the parallax barrier to separate the images received by the left eye and the right eye respectively to show a 3D image. The improvement of this patent is that a striped LCD panel is used instead of a general parallax barrier. The LCD panel also is able to switch between the 2D-image and the 3D-image modes.
With reference to FIG. 7, the device suffers from the following drawbacks:                {circle around (1)} high cost; and        {circle around (2)} non-continuous viewer tracking.        
To overcome the shortcomings, the present invention tends to provide an improved display device to mitigate and obviate the aforementioned problems.